1,1-Dichloro-1-fluoroethane and 1-chloro-1,1-difluoroethane may be produced by the liquid phase hydrofluorination of 1,1,1-trichloroethane. The reactor effluent contains, principally, these hydrochlorofluorocarbons and any hydrogen fluoride in excess of the stoichiometric amount required for complete reaction of 1,1,1-trichloroethane. While a variety of catalysts have been proposed for catalyzing the reaction, the system is sufficiently reactive to render a catalyst unnecessary.
U.S. Pat. No. 3,833,676 describes a non-catalytic batch process for fluorinating 1,1,1-trichloroethane with hydrogen fluoride. High hydrogen fluoride/1,1,1-trichloroethane ratios are recommended for maximizing conversion of 1,1,1-trichloroethane.
The process of U.S. Pat. No. 3,833,676 suffers from several disadvantages. Productivity is limited by the batchwise nature of the production scheme disclosed in said patent. A large excess of hydrogen fluoride remains in the reaction product. While U.S. Pat. No. 3,833,676 prefers a molar ratio of hydrogen fluoride to 1,1,1-trichloroethane in the range of between about from 4 to 30, reaction rate is slow, implying that high selectivity for 1,1-dichloro-1-fluoroethane is impossible, at the lower ratios. Presumably, phase separation occurs at lower HF/1,1,1-trichloroethane molar ratios when the reaction is operated in batchwise fashion as disclosed in U. S. Pat. No. 3,833,676.
Various patents describe processes in which reactants are introduced into a reactive liquid phase, and products are withdrawn as gases. See, e.g. U.S. Pat. Nos. 2,450,414 and 2,058,453. However, such systems have not been heretofore applied to the reaction of 1,1-trichloroethane and hydrogen fluoride, to produce 1,1-dichloro-1-fluoroethane, or mixtures of 1,1-dichloro-1-fluoroethane and 1-chloro-1,1-difluoroethane.